Margot Seitelman (1928 – 1989) was the long-serving first executive director of American Mensa, from 1961 (shortly after American Mensa's formation) until her death in 1989. The offices of the organization were originally in her apartment.

The American branch of Mensa International started forming in 1959. Two years later, it was incorporated, and began outgrowing its all-volunteer status, and needed a paid employee to manage its affairs. The original Mensa organization in Britain had set a model of having a housewife manage the organization out of her home. Thus, when Seitelman answered Mensa's advertisement in The New York Times, she appeared to be an excellent match. She ran Mensa out of her Brooklyn apartment.[2][3]

Her title is variously given as Director, Executive Secretary, and Executive Director.

Later, when the organization outgrew her ability to manage it part time out of her home, her duties were expanded to full time stewardship, and an office suite was rented – though still in the same building in which she lived.[2]

In her 28 years as an employee, she became affectionately known as the mother of American Mensa, outlasting all its elected officials.[3]

Seitelman died of cancer on 5 November 1989, at age 61, in Manhattan. At the time, she still held the Executive Director position for American Mensa. After her death, the organization moved its headquarters to Arlington, Texas and greatly expanded the staff.[4]